Studies on the Factors Affecting the Release of Organic Matter By Skeletonema Costatum (Greville) Cleve in Culture

1973 ◽  
Vol 53 (4) ◽  
pp. 937-956 ◽  
Author(s):  
L. Ignatiades ◽  
G. E. Fogg
Keyword(s):  
Organic Matter ◽  
Skeletonema Costatum ◽  
Physiological Activity ◽  
Marine Phytoplankton ◽  
Low Light ◽  
Factors Affecting ◽  
Light Intensities

A few studies on the excretion of organic matter by marine phytoplankton in culture have been reported (Guillard & Wangersky, 1958; Wangersky & Guillard, 1960; Stewart, 1963; Hellebust, 1965). Eppley & Sloan (1965) reported extensive excretion in Skeletonema costatum (Greville) Cleve cultures as they approached senescence and emphasized that excretion is inversely proportional to the physiological activity of cells. Hellebust (1965) demonstrated the release of high amounts (up to 38% of the carbon assimilated) of organic matter by Sk. costatum cells exposed to low light intensities. It is apparent that more knowledge is needed in order to define the intra- and extracellular factors affecting the excretion.

Factors affecting growith and distribution of kauri (Agathis australis Salisb.) I. Effect of light on the establishment of Kaura and of Phyllocladus trichomanoides D.Don

1959 ◽  
Vol 7 (3) ◽  
pp. 252 ◽  
Author(s):  
RL Bieleski
Keyword(s):  
Light Intensity ◽  
Frequency Distribution ◽  
High Light Intensity ◽  
High Light ◽  
Low Light ◽  
Factors Affecting ◽  
Light Intensities ◽  
Seedling Distribution ◽  
Conifer Seedling ◽  
Effect Of Light

A method for determining the effect of light on seedling distribution in the field is described. It can be applied when seedling frequencies are as low as 1/m2. The frequency distribution of light intensities occupied by seedlings in a quadrat is compared with the frequency distribution of light intensities measured on a grid in the quadrat. This method was used to study the effect of light intensity on the establishment of two New Zealand gymnosperms, kauri (Agathis australis) and Phyllocladus trichomanoides, in the nursery community, a semimature Leptospermum scoparium – L. ericoides associes. Kauri and Phyllocladus did not occur at light intensities below 0.015 and 0.018 full daylight respectively. This limitation appeared to be due to the low light intensity presumably limiting photosynthesis. Kauri, but not Phyllocladus, also showed a high light intensity limit, at 0.30 full daylight, above which seedlings did not establish. Reasons are given for considering this as an indirect effect, probably through related solar heating affecting soil temperature or moisture. The optimal light intensity for kauri and Phyllocladus seedling establishment was close to the modal light intensity under the Leptospermum community: Leptospermum spp. were incapable of regenerating under their own cover. These two reasons appear to explain the suitability of the Leptospermum community as a nurse crop for the two conifer seedling species.

Marine Phytoplankton Photosynthesis as a Function of Light Intensity: A Comparison of Methods

1964 ◽  
Vol 21 (1) ◽  
pp. 159-181 ◽  
Author(s):  
C. D. McAllister ◽  
N. Shah ◽  
J. D. H. Strickland
Keyword(s):  
Cell Division ◽  
Skeletonema Costatum ◽  
Algal Growth ◽  
Net Photosynthesis ◽  
Growth Conditions ◽  
Marine Phytoplankton ◽  
Fluorescent Light ◽  
Particulate Carbon ◽  
Gross Photosynthesis ◽  
Light Intensities

An apparatus is described in which the constant for exponential algal growth has been determined as a function of light at controlled temperature. Studies were made of bacteria-free cultures of Skeletonema costatum and Dunaliella tertiolecta grown at the optimum temperature for cell division in media with and without adequate nitrate and phosphate. Less complete studies were made of the behaviour of Monochrysis lutheri and Amphidinium carteri. In all experiments the growth constants were determined at known light intensities, expressed in the energy units, langlies/minute, using light of a known spectral distribution similar to sunlight shining through a few metres of coastal sea water.Growth constants were determined for the following processes: increase of cellular carbon, chlorophylls a, b or c, carotenoids, cell numbers and photosynthesis measured both by oxygen evolution (net and gross) and by the uptake of C-14 labelled carbonate.The rate of maximum photosynthesis occurred when the illumination reached about 0.1 ly/min and little or no light inhibition occurred when the intensity was increased to as high as 0.4 ly/min. Respiration was about 10% of maximum gross photosynthesis. This fraction increased when cells were nitrogen deficient but decreased in phosphate deficient cultures because a phosphate shortage inhibited respiration more severely than photosynthesis.Gross photosynthesis at low light intensities was proportional to the total number of molecules of all plant pigments added together, irrespective of species or of culturing conditions. By contrast, the rate of maximum gross photosynthesis was poorly related to pigment composition, the best correspondence being with the amount of chlorophyll a in the cultures.The uptake rate of C-14 varied with time. There was an apparent "leakage" of labelled organic matter which eventually reached a near-equilibrium with 14CO2 uptake, after which the C-14 method measured the production of particulate carbon but not necessarily net or gross photosynthesis. The rate of particulate carbon production was the same as that of cell division but about 40% less than net photosynthesis in cultures of Skeletonema. Agreement between C-14 rates and net photosynthesis was better in cool-white fluorescent light than in the imitation submarine sunlight used in this work. At high light intensities there was apparently no excretion from Dunaliella "shade" cells but when these became changed to "sun" cells they behaved more like Skeletonema.Various observations are recorded of the effect of growth conditions on cell composition, especially with regard to pigments.The relatively low C-14 rates found with Skeletonema costatum may be explicable in part by an abnormally low counting efficiency for this species even when present as a "weightless" source but the problem requires further study.

Extracellular products of phytoplankton photosynthesis

1965 ◽  
Vol 162 (989) ◽  
pp. 517-534 ◽  
Keyword(s):  
Organic Matter ◽  
Total Carbon ◽  
Trophic Relationships ◽  
Low Light ◽  
Light Intensities ◽  
Wide Range ◽  
Different Types ◽  
Extracellular Products ◽  
Total Primary Productivity

Following exposure in situ for periods of 3 to 24 h of samples of lake or sea waters to which 14 C-bicarbonate had been added, radioactivity was found in dissolved organic matter in the water as well as in the cells of phytoplankton. The amount in the water was between 7 and 50% of the total carbon fixed in the photic zone of the water column. This production of extracellular 14 C-labelled organic matter was found under a wide variety of conditions and with many different types of phytoplankton community. It thus seems likely that the widely used method, in which fixation of 14 C in particulate matter only is determined, under­estimates total primary productivity. The labelled organic substances in the water are probably liberated by intact photosynthesizing cells rather than by breakage of cells during filtration. Glycollic acid is likely to be one of the principal substances concerned. Over a wide range of light intensities liberation of extracellular products by a given phytoplankton population was proportional to the amount of carbon fixed in the cells, except that it tended to be relatively greater at low light intensities (< 1 kilolux) and at light intensities high enough to inhibit photosynthesis ( > 50 kilolux), when as much as 95% of the total organic 14 C might be extracellular. Population density, period of exposure to 14 C-bicarbonate and species differences also affect the extent of excretion. The implications of extensive liberation by phytoplankton of extracellular products of photosynthesis for our understanding of the trophic relationships in aquatic habitats seem to be considerable.

Studies on the Factors Affecting the Release of Organic Matter By Skeletonema Costatum (Greville) Cleve in Field Conditions

1973 ◽  
Vol 53 (4) ◽  
pp. 923-935 ◽  
Author(s):  
L. Ignatiades
Keyword(s):  
Organic Matter ◽  
Marine Environment ◽  
Skeletonema Costatum ◽  
Field Conditions ◽  
Limited Data ◽  
Factors Affecting

At the present time only limited data about the release of organic matter by phyto-plankton in the marine environment are available (Antia, McAllister, Parsons, Stephens & Strickland, 1963; Fogg, Nalewajko & Watt, 1965; Hellebust, 1967; Jitts, 1967; Home, Fogg & Eagle, 1969; Anderson & Zeutschel, 1970; Thomas, 1971; Samuel, Shah & Fogg, 1971).

scholarly journals A Quantitative Analysis of Factors Influencing Organic Matter Concentration in the Topsoil of Black Soil in Northeast China Based on Spatial Heterogeneous Patterns

2021 ◽  
Vol 10 (5) ◽  
pp. 348
Author(s):  
Zhenbo Du ◽  
Bingbo Gao ◽  
Cong Ou ◽  
Zhenrong Du ◽  
Jianyu Yang ◽  
...  
Keyword(s):  
Land Use ◽  
Organic Matter ◽  
Soil Erosion ◽  
Soil Type ◽  
Northeast China ◽  
Black Soil ◽  
Factors Affecting ◽  
Soil Zone ◽  
Rainfed Farming ◽  
Study Results

Black soil is fertile, abundant with organic matter (OM) and is exceptional for farming. The black soil zone in northeast China is the third-largest black soil zone globally and produces a quarter of China’s commodity grain. However, the soil organic matter (SOM) in this zone is declining, and the quality of cultivated land is falling off rapidly due to overexploitation and unsustainable management practices. To help develop an integrated protection strategy for black soil, this study aimed to identify the primary factors contributing to SOM degradation. The geographic detector, which can detect both linear and nonlinear relationships and the interactions based on spatial heterogeneous patterns, was used to quantitatively analyze the natural and anthropogenic factors affecting SOM concentration in northeast China. In descending order, the nine factors affecting SOM are temperature, gross domestic product (GDP), elevation, population, soil type, precipitation, soil erosion, land use, and geomorphology. The influence of all factors is significant, and the interaction of any two factors enhances their impact. The SOM concentration decreases with increased temperature, population, soil erosion, elevation and terrain undulation. SOM rises with increased precipitation, initially decreases with increasing GDP but then increases, and varies by soil type and land use. Conclusions about detailed impacts are presented in this paper. For example, wind erosion has a more significant effect than water erosion, and irrigated land has a lower SOM content than dry land. Based on the study results, protection measures, including conservation tillage, farmland shelterbelts, cross-slope ridges, terraces, and rainfed farming are recommended. The conversion of high-quality farmland to non-farm uses should be prohibited.

A laboratory study of vertical migration

1955 ◽  
Vol 144 (916) ◽  
pp. 329-354 ◽  
Keyword(s):  
Light Intensity ◽  
Vertical Migration ◽  
Time Course ◽  
Tap Water ◽  
Low Light ◽  
Overhead Light ◽  
Light Intensities ◽  
Orientation Response ◽  
Reduced Light ◽  
Characteristic Maximum

In a tank filled with a suspension of indian ink in tap water, a population of Daphnia magna will undergo a complete cycle of vertical migration when an overhead light source is cycli­cally varied in intensity. A ‘dawn rise’ to the surface at low intensity is followed by the descent of the animals to a characteristic maximum depth. The animals rise to the surface again as the light decreases, and finally show a typical midnight sinking. The light intensities at the level of the animals in this experiment are of the same order as those which have been reported in field observations; the time course of the movement also repeats the natural conditions in the field. The process is independent of the duration of the cycle and is related only to the variation in overhead light intensity. At low light intensity the movement of the animal is determined solely by positive photo-kinesis; the dawn rise is a manifestation of this, and is independent of the direction of the light. At high light intensities there is an orientation response which is superimposed upon an alternating positive (photokinetic) phase and a negative phase during which movement is inhibited. The fully oriented animal shows a special type of positive and negative phototaxis, moving towards the light at reduced light intensities and away from it when the light intensity is increased. In this condition it follows a zone of optimum light intensity with some exactness. Experiments show that an animal in this fully oriented condition will respond to the slow changes of intensity characteristic of the diurnal cycle, while being little affected by tran­sient changes of considerable magnitude.

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